To evaluate prognostic factors that may influence local control (LC) of T1N0 glottic cancer treated by primary radiotherapy (RT) with 6 MV photons. Methods We retrospectively reviewed the medical records of 433 consecutive patients with T1N0 glottic cancer treated between 1983 and 2005 by RT in our institution. All patients were treated with 6 MV photons. One hundred and seventy seven (41%) patients received 52.5 Gy in 23 fractions with 2.5 Gy/fraction, and 256 (59%) patients received 66 Gy in 33 fractions with 2 Gy/fraction. Results The median follow-up time was 10.5 years. The 10-year LC rates were 91% and 87% for T1a and T1b respectively. Multivariate analysis showed LC rate was adversely affected by poorly differentiated histology (Hazard Ratio [HR]: 7.5, p = 0.035); involvement of anterior commissure (HR: 2.34, p = 0.011); fraction size of 2.0 Gy (HR: 2.17, p = 0.035) and tumor biologically effective dose (BED) < 65 Gy 15 (HR: 3.38, p = 0.017). Conclusions The negative impact of anterior commissure involvement could be overcome by delivering a higher tumor BED through using fraction size of > 2.0 Gy. We recommend that fraction size > 2.0 Gy should be utilized, for radiation schedules with five daily fractions each week.
R E S E A R C HOpen Access Impact and relationship of anterior commissure and timedose factor on the local control of T1N0 glottic cancer treated by 6 MV photons * ChiChung Tong , KwokHung Au, Roger KC Ngan, SinMing Chow, FoonYiu Cheung, YiuTung Fu, Joseph SK Au and Stephen CK Law
Abstract Background:To evaluate prognostic factors that may influence local control (LC) of T1N0 glottic cancer treated by primary radiotherapy (RT) with 6 MV photons. Methods:We retrospectively reviewed the medical records of 433 consecutive patients with T1N0 glottic cancer treated between 1983 and 2005 by RT in our institution. All patients were treated with 6 MV photons. One hundred and seventy seven (41%) patients received 52.5 Gy in 23 fractions with 2.5 Gy/fraction, and 256 (59%) patients received 66 Gy in 33 fractions with 2 Gy/fraction. Results:The median followup time was 10.5 years. The 10year LC rates were 91% and 87% for T1a and T1b respectively. Multivariate analysis showed LC rate was adversely affected by poorly differentiated histology (Hazard Ratio [HR]: 7.5,p= 0.035); involvement of anterior commissure (HR: 2.34,p= 0.011); fraction size of 2.0 Gy (HR: 2.17, p= 0.035) and tumor biologically effective dose (BED) < 65 Gy15(HR: 3.38,p= 0.017). Conclusions:The negative impact of anterior commissure involvement could be overcome by delivering a higher tumor BED through using fraction size of > 2.0 Gy. We recommend that fraction size > 2.0 Gy should be utilized, for radiation schedules with five daily fractions each week. Keywords:T1N0 glottic cancer, radiotherapy, 6 MV, anterior commissure, Biologically effective dose
Background Laryngeal cancer is the third most common head and neck (H&N) cancer in Hong Kong. The agestandar dized incidence rate was 2.3 per 100,000 [1] and is com parable to those of other developed countries like USA, the Netherlands and Japan. In Hong Kong, around 95% of early glottic cancer (GC) patients were treated by pri mary radiotherapy (RT) alone [2]. There is extensive published data regarding manage ment of early GC treated by RT with Cobalt60 or 24 megavoltage (MV) photons beam, with local control (LC) rates ranging from approximately 8594% in T1N0 disease [35]. The reported treatment outcome of early GC by primary irradiation with 6 MV photons is limited and conflicting. Some authors reported comparable
* Correspondence: chichungtong@hkcr.org Department of Clinical Oncology, Queen Elizabeth Hospital, 30 Gascoigne Road, Kowloon, Hong Kong
results with lower energies [6,7] whereas others raised concern about a poorer outcome [8,9]. We present our institution’s experience in this report.
Methods Patient characteristics In mid 2010, we conducted a retrospective analysis of laryngeal cancer patients referred to our center for radi cal treatment over a 26 year period between January 1983 to December 2005. A total of 1256 consecutive patients were identified. This retrospective study was approved by our Institutional Review Board and Ethics committee. According to the Hong Kong Cancer Regis try, about a quarter of all laryngeal cancer cases diag nosed in Hong Kong over that period were treated in our institution. Out of the 1256 patients, there were 433 previously untreated patients with T1N0 GC.